Holley EFI System - A Stroke Of Efi Genius

We Test The Hye-Tech Performance 391 Stroker With Holley's New EFI

One of the really cool things about magazine engines is that we continually get to "revisit" them and monitor their progress. One such project was first seen in our June '01 issue, called "A Stroke of Genius." It involved the buildup of a 391-cid small-block using an effective, yet unconventional, offset-ground crankshaft and rods with the small 327 journal size to yield the extra cubic inches. We followed the buildup over the next two issues and finished with a dyno flogging at Vrbancic Brothers Racing Engines in the August '01 issue.

Then, we revisited the 391 once again in the November '01 issue where we abused it on the dyno in an attempt to see just how much nitrous we could pump into a street motor before it blew up. That test revealed some interesting results. The most important thing we got out of it was that nitrous motors really need some high-octane race gas to live with anything above a 150hp shot. Due to our insistence on running only 91-octane fuel, the engine broke and was summarily shelved for several months until we could figure out a cool approach for its next story. That begins now.

We pitched the idea of setting up the "Genius" stroker to test some Holley street EFI equipment to its original builder, Hye-Tech Performance in La Puente, California. They agreed that it would be a cool idea and began rebuilding the engine near to its original, pre-nitrous-destruction specs. That means a new set of 10.4:1 JE pistons were hung off the original C.A.T. Power 5.7-inch rods with a new Total Seal gapless ring set replacing the damaged pieces. Clevite supplied some new rod and main bearings, and the bottom end was complete.

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Hye-Tech Performance rebuilt the long-block using all the same components as before, including the same Valley Head Service-ported Holley aluminum cylinder heads. The only component changed was the Lunati cam.

Since EFI is currently the hot ticket when it comes to making everyday-reliable street power, we thought we'd add a new Holley Stealth Ram to this stroker to see what it's made of. One thing that had to be changed to work best with the new EFI system was the cam because the solid nitrous grind we had in it before just wouldn't do. So a call was made to Lunati for one of their hydraulic roller EFI grinds, since that'd be a cool way to cruise. With the new cam in the block we tackled installing the Holley Stealth Ram kit. After reading the Holley instruction manual, figuring out where each of the multitude of wires plugged in was fairly simple. Then, to see what this thing could do, we trucked it back over to Vrbancic Brothers Racing and bolted it onto the DTS dyno for its third flogging.

There's another benefit to building magazine test engines. When the people that make the parts we're testing, Holley in this case, want to be sure that we get the best results possible, they'll send a representative out to "supervise" our test sessions. We love that because it means we've got another more-experienced soul in the dyno cell to bounce questions and ideas off of, and if we run into problems, they'll have a much better chance of getting them corrected back at the shop than we would on our own.

For this test, Holley's Doug Flynn came armed with his mighty laptop and was able to tune some impressive figures from our otherwise docile Mouse. The thing to remember with the Stealth Ram kit is that it's not designed to make gobs of power. Rather, its sole purpose is to give its owner smooth cruising, reasonable economy, and easy tunability, all in a package that anyone with a toolbox and a laptop could install and tune. Don't get us wrong; at first this thing was a bit hard to figure out, but once we got all the wires plugged into their correct spots and fired it up, Doug showed us that dialing it in was a piece of cake.

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Holley EFI System - A Stroke Of Efi Genius

Hye-Tech Performance rebuilt the long-block using all the same components as before, including the same Valley Head Service-ported Holley aluminum cylinder heads. The only component changed was the Lunati cam.

Installing the Stealth Ram intake manifold was no more difficult than installing a regular four-barrel intake, except it has a removable top. We used antiseize/thread sealer on all intake manifold bolts.

The injectors get pushed into the cast-in bungs on the intake manifold, and the fuel rails gets pushed on top. Spray some lubricant on the O-rings of each injector and they'll be much easier to install. Make sure to tighten the four bolts that hold the rail in place, otherwise you'll have a massive fuel leak.

The plenum box sits on top of the runners and needs to have this vacuum hole plugged if you're not running power brakes. Don't forget to plug it or you'll have a major vacuum leak!

This is the power we made using a relatively small hydraulic roller cam with 1.6:1-ratio rockers on the intakes and 1.5:1 rockers on the exhaust. Total timing was set at 36 degrees, and we ran nothing but 91-octane pump gas.

The twin throttle body gets bolted onto the plenum next and the Idle Air Control Valve (IAC) is secured below it.

Note how the horsepower smoothly kept climbing until it peaked and, even then, just barely began to taper off. This would make one very smooth-pulling street engine. Also check out how thislittle Rodent made over 400 lb-ft of torque at 2,600 rpm and never dropped below 400 until 6,000 rpm! Put an overdrive trans behind this thing and it'll haul a house!

Two gaskets are supplied to seal the plenum to the base. Don't use any sealer on them. Just four stainless steel bolts are needed to hold the top down.

The throttle position sensor (TPS) goes on the side of the throttle body and tells the computer how far the throttle blades are open. This can be roughly translated into how much power your foot wants the engine to make.

The Holley ECU monitors coolant temp as well as both ambient and manifold air temp. It can also be programmed to turn on or off things like electric fans and bump up idle speed when you turn on your A/C, since it now knows how hot the engine is and how well it idles.

Before randomly trying to figure out where each wire goes, sit down and read through the entire instruction manual. You might find it difficult to read at first, but it'll all make sense once you're trying to plug things in.

Not only does EFI have lots of electrical connections, there are also lots of vacuum connections and even some vacuum connections that go to electrical connections! The Manifold Air Pressure (MAP) sensor is one of them. In non-boosted engines like this one, a 1-BAR MAP will always read intake manifold vacuum, instead of pressure.

Sitting to the left is Holley's EFI expert, Doug Flynn, who flew out to California to help us tune this thing perfectly. Dyno operator and co-owner of Vrbancic Brothers Racing, George Vrbancic, is actually pretty well up to speed on tuning EFI motors and was even able to show Doug a thing or two.

Even though the Holley ECU controls the timing advance curve, you still have to set it first the old-fashioned way. We set ours to a max 36 degrees and tweaked the distributor's curve with the computer to get the best power. There are no springs or advance mechanism in the Holley distributor to wear out, either.

We had to try one old hot rodder's trick to see if we could squeeze out more power. We swapped the Lunati 1.5:1 intake rockers with some 1.6:1-ratio rockers and found just a hair more power.